The present invention relates to xe2x80x9chigh dryxe2x80x9d formulations for preparing paints and coatings in general. It relates in particular to xe2x80x9chigh dryxe2x80x9d compositions based on fluorine containing polymers. As xe2x80x9chigh dryxe2x80x9d we mean formulations wherein the solvent is 20% by weight at most, preferably 10% by weigh. More particularly the object of the present invention relates to compositions suited for top coating, in particular in the car field, endowed with optimal capacity of adhesion to pigment ed bases, high hardness, protective an d antispot properties, scratch resistance, weather-proof and in particular resistant to UV radiation. Moreover the compositions must be usable in field applications, that is outside, assuring high aesthetic qualities, such as high gloss, image definition (DOI), together with the protective function and utilize a little solvent thus reducing the environmental impact. High dry formulations can be used in a range of temperatures generally from 10xc2x0 C. to 50xc2x0 C. This however depends on the crosslinking system, as well known, for instance melamines and blocked diisocyanates require higher temperatures.
The use of fluorine containing polymers for preparing coatings is known. These polymers are endowed with very good chemical, thermal and UV resistance and oleo- and water repellence. Known formulations for coating, having a fluorine containing basis, are for instance chlorotrifluoroethylene (CTFE) copolymers with hydrogenated vinylether or vinylesters; or VDF (vinylidenefluoride) polymer or copolymers with tetrafluoroethylene and/or hexafluoropropylene. The former are for instance LUMIFLON(copyright) and CEFRAL(copyright), the latter are commercialized for instance as KYNAR(copyright) and TECNOFLON(copyright). The main drawback of these fluoropolymers is that they are employed at high dilutions, even of 90% by weight of solvent. This leads to high costs for eliminating the solvents, since the solvents needed for preparing the formulations of these fluorine containing polymers have a high environmental impact.
In the case of TECNOFLON(copyright)-based coatings, chlorofluorocarbon solvents, which will be no longer used according to the laws of all countries, are presently used. In conclusion, these fluorine containing polymers even though endowed with the indicated excellent properties, cannot be used for high dry formulations.
The use of partially fluorinated copolymers is also known in the art, for instance perfluoropolyethers of elastomeric or filming type, are crosslinkable depending on the molecular weight and on the ratio between fluorine containing part and hydrogenated part.
However these products need to be used at high dilutions. Moreover, weather stability is not good. Therefore it is not possible to prepare high dry formulations from these products.
Coatings based on polyesters from perfluoropolyethers and coatings based on perfluoropolyethers containing acrylic groups are also known. One can see European patent applications 622353 and 622391 in the name of the Applicant. These products give good coatings and allow the use of less solvent than the products of the art indicated above. However it is not possible to obtain high dry formulations from these products since they require an amount of solvent of about 50% by weight.
The use of water coatings is also known. These formulations contain a low amount of solvent, of about 10%, whereby they could fall within high dry formulations, however they are endowed with low chemical resistance and moreover do not show the high aesthetic and mechanical properties, such as the gloss and the hardness that the high quality coatings must have.
Solvent-less coatings are also known, that is homogeneous bicomponent compositions without solvents or having a limited amount of solvents, applicable by means of traditional techniques and therefore endowed of minimum environmental impact. Epoxy resins can be mentioned. These resins however lead to poor coatings (coatings of inferior quality) from the aesthetic point of view. For instance the gloss of the coatings is of the order of 10-20 at 60xc2x0 C. according to ISO 2813 standard. These compositions, however, do not yield reduced coating thicknesses, lower than 50 xcexc, as required for top coating. Moreover the finishing of these products is not very good.
Object of the present invention is obtaining xe2x80x9chigh dryxe2x80x9d formulations based on fluorine containing polymers capable of giving crosslinked films having the combination of properties indicated above: very good chemical, mechanical, thermal properties and resistance to UV radiations, usable also for applications on the field, very good aesthetic and durability properties, scratch and spot resistance.
The Applicant has unexpectedly and surprisingly found that it is possible to prepare xe2x80x9chigh dryxe2x80x9d formulations based on fluoropolyethers if functionalized fluoropolyethers, as defined hereinunder, are used.
It has been surprisingly found that the polymers based on fluoropolyethers as defined be low do give xe2x80x9chigh dryxe2x80x9d formulations since they require the addition of small amounts of solvent, of about 10% by weight and generally lower than 20% by weight.
Object of the present invention are high dry formulations of fluorine containing polymers for preparing paints and coatings wherein the fluorine containing polymers are based on fluoropolyethers comprising a fluorine containing part RF and optionally a hydrogen containing part RH, the bonds joining the fluorine containing part to the hydrogen containing one being an ether, Cxe2x80x94Oxe2x80x94C, bond the terminals Txe2x80x2 being such as to render bi or polyfunctional the structure and thus making possible the crosslinking reaction, the hydrogen containing part RH not containing groups capable of linking by means of hydrogen bonds to basic acceptors.
More in detail, preferred are the fluorine containing products which can be represented with the formula
Txe2x80x2xe2x80x94(RH)xxe2x80x94RFxe2x80x94(RH)xxe2x80x94Txe2x80x2xe2x80x83xe2x80x83(I)
wherein
RF is 
wherein Rf is a fluoropolyether chain, Y and Yxe2x80x2 being same or different from each other and being F or CF3 
x is 0 or an integer from 1 to 10, preferably from 1 to 3;
RH is a linking bivalent radical, of linear aliphatic typexe2x80x94(CH2)mxe2x80x94, m being an integer from 1 to 20, or of (alkylene)cycloaliphatic type or of (alkylene)aromatic type, optionally having also heteroatoms on the ring or in chain, the number of carbon atoms being from 3 to 20 for the cycloaliphatic compounds, and from 5 to 30 for the aromatic ones; the RH group can also be a mixture of the types indicated:
Txe2x80x2=xe2x80x94(CH2CH2O)nxe2x80x94RH)xxe2x80x2xe2x80x94T, wherein n is 0 or an integer from 1 to 6, preferably from 1 to 2;
xxe2x80x2 is 0 or an integer from 1 to 10, preferably from 1 to 3, xxe2x80x2 can be different from x; and
T being hydrogen or a terminal capable of rendering bior polyfunctional the structure such as to make it reactive towards both ionic and radical crosslinking agents.
In particular terminals T are preferably of the type: 
In particular the following groups must be absent from the hydrogen containing part RH: xe2x80x94COOH, xe2x80x94NHxe2x80x94COOxe2x80x94; xe2x80x94NHxe2x80x94COxe2x80x94NHxe2x80x94; xe2x80x94OH; xe2x80x94NH2; xe2x80x94NHxe2x80x94; COxe2x80x94NHxe2x80x94.
The radical Rf of number average molecular weight Mn comprised, preferably, from 500 to 5000, more preferably from 700 to 1500, represents a fluoropolyether chain bifunctional radical, comprising as repetitive units sequences of one or more oxyfluoroalkylene units of the type 
wherein R4 and R5 have the meaning indicated hereafter.
It was unexpectedly found that the fluoropolymers of the present invention by addition of small amounts of solvent lead to the formation of solutions having an extremely low viscosity, generally of the order of 50-300 cPoise at room temperature.
It is even more surprising that amounts of about 2-3% by weight of solvents, selected from those generally used in the paints field are sufficient for obtaining solutions having very low viscosities such as to render them easily utilizable.
The preferred compounds of the formula I are the following: xe2x80x83RF[(CH2)6xe2x80x94CH(CH2Oxe2x80x94CH2xe2x80x94CHxe2x95x90CH2)2]2
Generally utilizable solvents are those broadly used in the field of paints. They are fluorine containing solvents containing hydrogen, ketones, esters of heteroalcohols, aromatics. Methyl ethyl ketone, methyl isobutyl ketone, ethyl or butyl acetate, cellosolve acetate, propylenglycolmethylether acetate, xylene are preferred. Chlorofluorocarbons not containing hydrogen are excluded as solvents.
The crosslinking agents used are the commercial ones and however the ones well known for the crosslinking of the crosslinkable functional groups. For instance the polyhydroxylated products of formula (I) are crosslinkable with melamine resins, with weight ratios comprised between 70:30 and 90:10, preferably 80:20, of the polyhydroxylate compound to melamine; the crosslinking temperature is around 130-150xc2x0 C.
The films obtained are homogeneous and transparent, of good hardness and hydrolysis resistant.
Alternatively the polyhydroxylated polymers are cross-linkable with polyisocyanates containing isocyanurate rings, or using suitable polyisocyanate prepolymers based on isophorondesocyanate (IPDI), toluenediisocyanate (TD), hexamethylendiisocyanate (HMDI), etc. in the presence of metal or amine catalysts, at room temperature or higher, using a NCO/OH ratio for instance from 1/1 to 1.5/1.
Blocked polyisocyanates obtainable from the polyisocyanates indicated above by reaction, for instance, with phenols or ketoxime can be also used. Other kinds of crosslinking are obtained using conventional organic peroxides, for instance, di-ter-butylperoxide, lauroylperoxide, benzoylperoxide.
Other non-peroxide radical initiators, such as for instance AIBN (azabisisobutyronitrile), can also be used.
The excellent properties of viscosity, together with the good compatibility with the solvents of current use in the field of paints and with the various crosslinking agents of paints make the perfluoropolyether polymers of the present invention suitable for formulating high dry paints endowed with good optical and mechanical properties.
The high gloss, high image definition, high adhesion to the various types of supports, good hardness and elasticity in addition to the optimal thermal, chemical and hydrolytic resistances, can be cited.
The advantage obtainable with the compositions of the present invention consists in that very small amounts of solvent are utilized, therefore with a remarkable reduction of the environmental impact and consequently of costs for eliminating solvents and recovery thereof.
The fluorine containing products of the present invention have a very good crosslinking density and then very good mechanical properties and resistance to swelling.
In particular the fluoropolyethers of Rf type utilizable according to the present invention can be of the following types, indicating the repetitive units of the chain:
a) xe2x80x94(C3F6O)mxe2x80x2 (CFYO)nxe2x80x2xe2x80x94 wherein the unit (C3F6O) and (CFYO) are perfluorooxyalkylene units statistically distributed along the chain; mxe2x80x2 and nxe2x80x2 are integers such as to give the molecular weight indicated above, and mxe2x80x2/nxe2x80x2 is comprised from 5 to 40, when nxe2x80x2 is different from 0; Y is equal to F or CF3; nxe2x80x2 can be also 0; 
wherein pxe2x80x2 and qxe2x80x2 are integers such that pxe2x80x2/qxe2x80x2 varies from 5 to 0.3, preferably 2.7-0.5 and such that the molecular weight is the one indicated above; txe2x80x2 being an integer with the meaning of mxe2x80x2, Y=F or CF3; txe2x80x2 can be 0 and qxe2x80x2/qxe2x80x2+pxe2x80x2+txe2x80x2 lower or equal to 1/10 and the ratio txe2x80x2/pxe2x80x2 is from 0.2 to 6;
c) xe2x80x94CR4R5CF2CF2Oxe2x80x94 wherein R4 and R5 are same or different from each other and selected from H, Cl, the molecular weight being that indicated above, a fluorine atom of the perfluoromethylene unit can be replaced by H, Cl or perfluoroalkyl.
The indicated fluoropolyethers are obtainable with the processes well known in the art, for instance, U.S. Pat. Nos. 3,665,041, 2,242,218, 3,715,378 and European patent EP 239,123. The functionalized fluoropolyethers are obtained for instance according to EP Patents 148,482, U.S. Pat. No. 3,810,874.
The fluoropolyethers of the present invention, in particular the fluorine containing polymers of formula (I) are obtained from the functionalized products, in particular from those with hydroxylic ending, according to the process indicated hereinunder.
The functionalized fluoropolyethers according to the present invention can be mixed in various ratios with bi or polyfunctional polyols having a hydrogen containing basis, for instance butanediol, trimethylolpropane, pentaerithrol. The ratio in equivalents of the hydrogen containing polyol to the fluorine containing polymers of the invention varies from 0.1 to 5, with the proviso that the hydrogen containing polyols are soluble in the formulation. In this way blends having specific properties depending on the particular type of the desired coating, are obtained.
The process for preparing the functionalized perfluoropolyethers of the present invention comprises: etherification of fluoropolyether having hydroxilic ends by salification of fluoropolyether and nucleophilic reaction with alkyl or aryl dihalides or pseudohalides, obtaining a fluorine containing polymer Axe2x80x2) of formula corresponding to (I) wherein Txe2x80x2 is replaced by X, the terminal X being susceptible of further nucleophilic attack; subsequent functionalization by nucleophilic attack of Axe2x80x2) with compounds containing carboanions to obtain the compound of formula corresponding to (I) containing the T terminal. Then optionally transformation of the functional T groups of ester type to other groups such as alcohols, amines, acids according to well known reactions.
The fluoropolyethers having hydroxyl terminals, for instance of Z2, P2 and A2 type (reported hereinunder) are obtainable according to known processes. For instance, Z2 is obtainable by reduction of the corresponding diester according to U.S. Pat. No. 3,810,874; A2 by salification of Z2 and reaction with ethylene oxide. Similarly one can obtain the compounds with fluorooxyalkylene units specified above for all the products Z2, P2 and A2 type.
In particular the process comprises:
1xc2x0 step) Direct etherification of the fluoropolyether with hydroxyl terminals, according to a pattern of nucleophilic substitution, Williamson type. In practice, the fluoropolyether (PFPE) with hydroxyl terminals is dissolved in a solution of potassium or sodium alcoholate in the corresponding alcohol, obtaining the alcoholate of the fluoropolyether. This is slowly added to t-butanol, or other solvent (for instance dioxane), containing a large excess of alkyl or aryl dihalide or pseudohalide.
Typically in this phase 1,4-dibromobutane, 1,5-dibromopentane, 1,6-dibromohexane, 1,8-dibromooctane, 1,10-dibromodecane and other higher or lower homologous compounds with bromides or chlorides terminals, can be used as reactants. 1,4-cyclohexanedimethanol dimesylate or ditosylate, mixtures of xcex1,xcex1xe2x80x2 dibromo or dichloro xylene or their pure isomers can also be used. The reaction temperature, depending on the halide reactivity, is comprised from +30 to +90xc2x0 C. and the reaction time is 1-8 hours. The fluoropolyethers, alkylated with conversion near 100%, are isolated by precipitation in H2O and filtration or distillation of by-products and reactants in excess. The residue or the filtrate corresponds to the general formula (A1) (specific product of A3 type defined further on), which is the same as (I) wherein the terminal is X (instead of T). X is still a reactive replaceable terminal being of the xe2x80x94Br, xe2x80x94Cl, xe2x80x94OSO2CH3, 
2xc2x0 step) Functionalization. By using active methylene compounds, such as for instance ethyl or methyl malonate or ethyl or methyl 1,1,2 ethanetricarboxylate when a higher final functionality is desired, or still polyols partially protected such as glycerol formal. The reaction of the PFPE adduct of formula A1, obtained in step 1, with active methylene compounds occurs easily and with high yields. The adduct (A1) is added slowly to an alcoholic solution for instance of sodium or potassium malonate, at a temperature of 40-80xc2x0 C. heating for 2-8 hours. The polyfunctionalized adduct I (specific product of the B2 type defined hereafter), is the product of formula (I) wherein the terminal T contains COOR wherein PFPE=R, as defined above, RH being the alkylene residue of the halide, R being CH2CH3 or CH3 of the malonate. This adduct I is isolated, with practically quantitative yields, by extraction with H2O and distillation of the solvents and reactants in excess. Optionally from the adduct I it can be obtained the release of other reactive functions, typically by reduction of the carboxylic esters for instance with LiAlH4/THF or by hydrogenation, or still by extension of the carboxyls with sterically hindered dialcohols (for instance neopentylglycol), by ammonolysis and reduction to give polyamine or simply by hydrolysis to give polyacids.
The adducts of type (I) obtained by polyfunctionalization with partially protected polyols, can lead to PFPE polyols for instance by releasing the acetal by hot treatment with mineral acids.
The partially fluorine containing resins so obtained having alcohol, amine, acid or other functionality, can be titrated easily for determining equivalent weight and functionality, for instance with the phenylisocyanate method or with alcoholic HCl or alcoholic KOH.
The final functionality of the resin of formula (I) so obtained is in any case 2 or higher, for instance 4 and 6.